Streamer manufacture

ABSTRACT

A seismic streamer comprises a cable harness inside an oil filled sheath. The sheath is a flexible plastic tube. The harness includes a plurality of hydrophones and associated electrical conductors, strain rope, spacers, and bulkheads. Prior to assembly with the sheath, the harness is wound on a reel inside a pressure vessel containing oil and air. One end of the harness is fed through a spigot at the side of the vessel below the oil level and connected to a free piston which is inserted into one end of the sheath. The sheath is attached to the spigot at the side of the vessel below the oil-air interface. The air in the tank is presurized placing the oil under pressure, and the harness and oil are fed to the sheath through the spigot. The pressurized oil forces the piston to move along the several hundred feet of sheath, pulling the harness into the sheath at a rate regulated by unwinding of the reel. The reel is actuated by a hydraulic motor. The piston is provided with a lubricator at its leading end, a pint or so of oil being placed in the sheath before it is attached to the spigot. The sheath is initially expanded by admitting air under pressure through a check valve at the other end of the sheath from the end attached to the spigot. A pressure relief valve maintains the desired air pressure in the sheath.

United States Patent n91 STREAMER MANUFACTURE [75] lnventor: A. C. Hill,Houston, Tex.

[73] Assignee: Teledyne Exploration Company, Houston, Tex.

[22] Filed: Nov. 23, 1973 [21] App]. No: 418,659

[52] US. Cl. 29/203 D; 29/169.5; 29/200 B; 29/241; 29/433, 15/104015 R[51] Int. Cl. (Mr

[58] Field of Search 29/1695, 203 MW, 203 D, 29/200 R, 200 B, 433, 241,244, 421 R;

l5/l04.16, 104.06 R, 104.05; 156/294;

Primary Examiner-C. W. Lanham Assistant ExaminerVictor A. Di PalmaAttorney, Agent, or Firm-Murray Robinson [451 May 27, 1975 [57] ABSTRACTA seismic streamer comprises a cable harness inside an oil filledsheath. The sheath is a flexible plastic tube. The harness includes aplurality of hydrophones and associated electrical conductors, strainrope, spacers, and bulkheads. Prior to assembly with the sheath, theharness is wound on a reel inside a pressure vessel containing oil andair. One end of the harness is fed through a spigot at the side of thevessel below the oil level and connected to a free piston which isinserted into one end of the sheath. The sheath is attached to thespigot at the side of the vessel below the oil-air interface. The air inthe tank is presurized placing the oil under pressure, and the harnessand oil are fed to the sheath through the spigot. The pressurized oilforces the piston to move along the several hundred feet of sheath,pulling the harness into the sheath at a rate regulated by unwinding ofthe reel. The reel is actuated by a hydraulic motor. The piston isprovided with a lubricator at its leading end, a pint or so of oil beingplaced in the sheath before it is attached to the spigot. The sheath isinitially expanded by admitting air under pressure through a check valveat the other end of the sheath from the end attached to the spigot. Apressure relief valve maintains the desired air pressure in the sheath.

11 Claims, 11 Drawing Figures PATENTED' 3,885,286

SHEET CZUF 4 PATENTEB HAY 2 7 I975 SHEEY EQUF 4 1 STREAMER MANUFACTUREBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to a method of and apparatus for inserting linearly distributedcomponents into an elongated housing and more particularly to theinsertion of mechanico-electrical transducers, electrical conductors,oil, and associated mechanical elements into a plastic tube to form astreamer.

2. Brief Description of the Prior Art In the course of conductingseismic surveys for the purpose of producing reflection profiles of theearths crust, it is a requirement that arrays of mechanicoelectricaltransducers or sensors, e.g., pressure sensitive hydrophones, be townedbehind the survey ship for the purpose of sensing reflected acousticsignals. These arrays are commonly referred to as streamers, and theyconsist of many discrete sensors electrically connected together andinstalled inside a sheath comprising a flexible tube (usually plastic)that is filled with oil. The overall length of the tubes variesaccording to the job requirement but most are made in sections that are150 to 300 feet in length. ln addition to sensors and oil, each sectioncontains many electrical conductors, strain member or members (usuallywire rope) and spacers that protect the internal components and causethe section to maintain a cylindrical shape. Each end of a section issealed with a liquid tight bulkhead that permits electrical feed throughof each conductor and mechanical continuity of the strain members. Thearrays are towed beneath the water and may be used singularly or incompound arrangements with sections attached end to end.

Streamer stuffing, i.e., the placement of the electrical and mechanicalcomponents (the harness) within the plastic tube and filling the tubewith oil or other fluids presents a considerable problem. Perhaps theoriginal method of installing a harness within a sheath was simply topull the sheath over the harness by hand, pulling on the sheath andharness with ropes.

Another and better method of streamer stuffing in use prior to thepresent invention involves the use of a long rigid pipe and a vacuumprocess. This method is generally as follows:

a. A pipe of the required length is furnished with an inside diameterslightly larger than the outside of the streamer to be constructed.

b. The streamer sheath is pulled inside the pipe with a winch and eachend is sealed against the mouth of the pipe. A vacuum is imposed on thespace between the sheath and the inside of the pipe. This expands theflexible sheath to a diameter larger than that of the harness andspacers that are to be installed inside. This also allows for openpassage through both ends of the sheath.

c. A steel cable is then placed completely through the sheath. One endof this cable is attached to the drum of a powered winch.

d. The harness which is made up of the sensors, conductors, spacers,strain members, etc., is then attached to the wire rope and is pulledinto the sheath with the winch.

e. After the harness has been drawn into the sheath, the vacuum isreleased and the sheath returns to its normal diameter and closes aroundthe cylindrical spacers of the harness.

f. The streamer section is then pulled by a winch or other means fromthe vacuum pipe.

g. Metal bands are clamped around each end of the section to form a sealbetween the sheath and the liquid tight bulkheads.

h. The section is then arranged in a relatively straight line on a flatsurface for oil filling.

i. The oil is pumped from a storage container into one end of thestreamer through a fitting provided for this purpose. A fitting in theother end allows the displaced air to escape. As the oil flows into thesheath, the cable must be elevated at the point of oil air interface tominimize trapping of air along the cable. This point of elevation mustbe maintained along the length of the cable as the filling progresses.

j. After the cable has been filled, the end with the air vent iselevated and the trapped air bubbles are walked" out by elevating thecable at one point and slowly moving this point of elevation toward theair vent. This may require several identical operations before all airis removed.

k. Each end is then secured and the section is completed.

Although the above described vacuum method is a considerable improvementover the earlier brute force pull over method, the vacuum method stillrequired a considerable amount of time and the forces imposed on theharness and sheath during the method were sufficient to be likely todamage them both. In addition, the requirement for a long straightvacuum pipe of a length equal to that of the streamer made it impossibleto use the method for replacement of a streamer sheath on board a boator ship of the size used in seismic work.

In an effort to overcome the aforementioned difficulties, TeledyneExploration Company devised a new method hereinafter referred to as thepressure method, according to which the sheath is expanded by internalair pressure and the harness is pulled through the sheath by a freepiston, oil under pressure being admitted to the end of the sheaththrough which the harness enters and providing the pressure for forcingthe piston along the interior of the sheathing. The harness is fed tothe sheathing from a reel; the reel is mounted in a pressure vessel inwhich also is contained both the oil and air to pressurize the oil. Thesheathing is attached to a spigot at the side of the pressure vesselthrough which emerges the harness and oil.

The above described pressure method provides a number of improvementsover the aforementioned vacuum method. These are as follows:

a. The new method, is much faster and cuts manufacturing time for thisprocess to about one-fourth of what it was previously.

b. Elimination of the need for a long straight vacuum pipe allowsreplacement of streamer sheaths aboard ship. This was not possiblebefore.

c. The harness and the oil are injected into the sheath simultaneouslyand the need to walk out air bubbles is eliminated.

d. This process minimizes the possibility of damage to the components ofthe harness during the sheathing process. The strong forces required inprevious winching methods sometimes impose damaging stresses andstrains.

e. The plastic sheaths used in manufacturing streamer sections areusually transparent. Observation of the progress of insertion of theharness is now possible.

Experiments using this general principle were conducted as early as1969. Development was continued sporadically from that time untilcertain features were added in December, I972, which made this methodpractical. It is now in use as a standard process by TeledyneExploration Company, Houston, Tex.

Prior to December I972, some of the features of the system were used inthe fabrication of streamer cables on an experimental basis. Thecontinued development of the system was made possible by the receipt oforders from customers that related to the resheathing of streamers. Itwas not practical or economically feasible to develop the system ortechnique without specimens to work with and funds to support thedevelopment. Several prototypes were built for experimentation duringthis period but were discarded as impractical. To the extent the use ofthe pre-December 1972 apparatus does not bar it from patent protectionand to any extent the inventorship may be the same as that named herein,Teledyne Exploration Company, assignee, desires to patent same herein.

SUMMARY OF THE INVENTION The original apparatus built by Teledyne wasdesigned to fill a l inch diameter streamer. A later version was builtseveral years ago. The present invention is an improvement upon theearlier Teledyne method and apparatus and incorporates the followingadditional features:

1. a hydraulically operated reel to feed off the harness to theadvancing free piston at a controlled speed.

2. a lubricator in advance of the free piston to prevent binding of thepiston. 3. air inlet and pressure relief valve means at the downstreamend of the streamer sheath through which the streamer is pressurized inadvance of the free piston.

BRIEF DESCRIPTION OF THE DRAWINGS For a detailed description ofapreferred embodiment of the invention reference will now be made to theaccompanying drawings wherein FIG. 1 is a partly schematic side view ofa streamer harness of a type that can be made in accordance with theapparatus and method of the invention;

FIGS. 2, 3 and 4 are fragmentary sections showing component portions ofa streamer comprising a sheathing and a harness of the type shown inFIG. 1;

FIGS. 5 and 6 together form a partly schematic horizontal sectionthrough apparatus in accordance with the invention, showing the streamersheath attached to the pressure vessel and the free piston putting theharness from the reel into the sheath;

FIGS. 7 and 8 together form a partly schematic vertical section of theapparatus of FIGS. 5 and 6 showing same prior to attachment of thesheath to the pressure vessel spigot;

FIG. 9 is a partly schematic side view of a streamer harness wound on areel in accordance with the invention;

FIGS. 10 and I] together form a side view of a godevil comprising (FIG.II) the lubricator provided according to the invention and theassociated free piston and (FIG. ID) the rear guide to which thestreamer harness is to be connected.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to FIG. 1 there isshown a harness section comprising a plurality of hydrophones 21, 23,25, 27, 29, with associated electrical conductors 31, 33, 35, 37, 39,strain rope 41, through electrical conductors 43, spacers, 45, 47, 49,51, and bulkheads 53, 55.

FIG. 2 shows the bulkhead 53 is sealed to the transparent flexibleplastic tube that forms sheath 6! by means of annular straps 63, 65extending around the sheath and holding it tightly to the bulkhead. Theinterior of the sheath around the harness is filled with oil 67.

Eyes 69, 71 extend from the bulkhead at opposite ends thereof to providemeans for making connection to strain rope 4. The strain rope togetherwith through conductors 43 and local conductors such as 31 extendthrough the spacers, such as 43, that separate the hydrophones.

As shown in FIGS. 3 and 4, each hydrophone streamer includes a couplingtransformer, such as 75, and responsive elements 77.

Referring now to FIGS. 5 and 6, there is shown a steel pressure vessel81 within which is a reel 82, shown in detail in FIG. 9. One end 78 ofthe vessel is removable for easy access to the interior. The reel ismounted for constant about a horizontal axis and is driven at controlledspeed by hydraulic motor 83. Wound on the reel is a streamer harness 84of the type shown in FIG. 1. The hydraulic motor 83 is supplied withhydraulic fluid under pressure at controlled rate of flow by controller85 which may be any suitable type.

Oil for the pressure vessel 81 is supplied from reservoir 86 byreversible electric pump 87. Electrical controller 88 governs the speedof pump 87. The pump is connected to the pressure vessel through pipe 89in which line there is a hand operated shut off valve 91.

The pressure vessel is supplied with air under pressure from a suitablesource, not shown, such as an air compressor, through line 93,adjustable pressure regulator 94, and valve 95. Regulator 94 exhauststhrough line 96.

The pressure vessel is interiorly lighted as shown at 19, and isprovided with a transparent inspection port 97. The pressure vessel isfunnel shaped and at the small diameter part of the funnel is a spigot98 which has a diameter slightly larger than the diameter of harness 84so that the harness can pass therethrough, e.g., into sheath 61.Preferably, the spigot 98 is connected to the pressure vessel by boltedflanges as shown at 99 so that different size spigots can be substitutedeasily.

As best shown in FIG. 7, the level of the oil 101 is above the spigot 98during operation of the equipment to stuff a streamer. To prevent oilfrom leaking out the spigot when the sheath is unconnected thereto, asshown in FIG. 8, the oil level may be lowered below the spigot byreversing pump 87. After the sheath 61 has been connected to the spigot,the pump 87 is run in a direction to bring the oil level up above thelevel of the spigot, preferably above the level of the harness wound onthe reel, so as to prevent the air 103 from escaping with the harnessthrough the spigot.

Referring now to FIGS. 6 and 8, 10, and 11 there is shown within sheath61 a go-devil Ill. The go-devil has a maximum relaxed outer diameterslightly larger than the inner diameter of sheath 61. The go-devilcomprises a fairly rigid plastic tube 113 having at its rear end a guidehub 115 adapted to be connected by a cable 117 to eye 69 on the harness.At the forward end of the tube 113 is a piston 119 having flexible liptype annular seals 120 at its trailing end. The seals are adapted tocontact and seal with the inner periphery of sheath 61. In advance ofpiston 119 is an oil spreader or lubricator 121 comprising a rotatablymounted hub 123 having one and preferably several overlapping helicalribs 125 extending thereabout adapted to contact the entire innerperiphery of the sheath 61. As the lubricator 121 rotates about the axisof tube 113, the entire inner surface of the sheath will be contactedwith oil.

Referring now to FIG. 6, at the end of sheath 61 is connected a valve131 comprising a body 135 adapted to fit within and be clamped insealing engagement with sheath 61 by straps 137. A passage 139 extendingaxially through body 135 leads to constant presure relief valve 141, anda side port 143 leads to an air admission check valve 145.

The apparatus which has been described can be operated in almost anyenvironment, e.g., on the deck of a boat, the only requirements being:available electric power, pressure air supply, and a supply of fluid forfilling the pressure vessel. The standard procedure for completing astreamer section using this apparatus is as follows:

a. The streamer harness 84 is placed through the spigot 98 and stored onreel 82. During this process the reel is powered by motor 83 andcontrolled by hydraulic valves 85. A short portion of the harness isleft extending out of the spigot 98.

b. The go-devil 111 is attached to the end of the harness and insertedinto the end of the sheath 61. A small amount, e.g. a pint, oflubricating oil is poured into the sheath before inserting the go-devil.

c. The sheath is slipped over the spigot 98 and secured to the spigot bymeans of metal bands or hose clamps 151.

d. The valve 131 is installed in the other end of the sheath and securedwith hose clamps 137.

e. Using control 88 and pump 87, oil or other fluid is transferred fromreservoir 86 into pressure vessel 81. The vessel is filled to a desiredlevel above the point at which the sheath is attached. At this point inthe operation, the pump 87 is shut off, and the oil line closed usingvalve 87.

f. Using adjustable regulator 94 the pressure within the chamber isincreased by introducing pressurized air from a compressor or othersource. This pressure is monitored at regulator 94 and shut off afterreaching a predetermined level for example 25 psi. The vessel is thensealed by closing valve 95.

g. Air pressure is applied through check valve 145 of the valve unit 137until pressure within the sheath 61 reaches a predetermined level forexample psi, as set by relief valve 141. This inflates the plasticsheath making it round and slightly larger than its normal diameter.This allows the go-devil to pass through and, because of the roundness,to seal more efficiently. The preset pop-off valve 141 maintains thedesired pressure ahead of the go-devil.

h. Next the reel is put into operation using external controller 85, andthe harness is pulled into the sheath by the attached piston clue toforces imposed upon it by the air pressure acting through fluid. As thepiston moves through the sheath, the sheath is filled with fluidsimultaneously. During the traverse of the harness, the lubricator 121at the leading end of the piston 119 is in contact with the inside ofthe sheath. lt rotates due to its shape and distributes the lubricatingoil on the inside of the sheath. This allows the piston to move freelyand also aids in sealing at this point of contact.

i. After the harness has been placed within the sheath the reel isstopped and metal bands or hose clamps are secured around the sheath ateach end. This seals the sheath to the liquid tight bulkheads.

j. The excess sheath is trimmed from each end of the streamer sectionand the operation is complete.

Several streamer sections can be connected together end to end inconnventional fashion to form a streamer of greater length if desired.

While a preferred embodiment of the method and apparatus of theinvention has been described and illustrated, modifications thereof canbe made by one skilled in the art without departing from the spirit ofthe invention.

1 claim:

1. Apparatus for assembling a seismic streamer comprising a pressurevessel containing a rotatably mounted reel adapted to have a seismicstreamer harness wound thereon,

said vessel being adapted to contain oil, adapted for filling a seismicstreamer sheath, and pressurized air over the oil, said vessel having anoutlet adapted to be connected to said sheath for a seismic streamer andthrough which a harness wound on the reel can extend, and

means for driving the reel at controlled speed to pay out the harness tosuch sheath.

2. Apparatus according to claim 1 having a seismic streamer harnesswound on the reel and having attached to the free end of the harness ago-devil comprising a piston adapted to seal with the inner periphery ofsaid sheath and a lubricator in advance of the piston.

3. Apparatus according to claim 2 in which the lubricator includes a hubhaving a plurality of circumferentially overlapping helical ribsthereabout.

4. Apparatus according to claim 3 wherein the hub is rotatably mountedabout the go-devil axis.

5. Apparatus according to claim 2 including a tubular seismic streamersheath connected at one end to the pressure vessel outlet and closed atthe other by a constant pressure relief valve, the godevil beingdisposed in said sheath, and a quantity of lubricating oil beingdisposed in said sheath between the piston and said relief valve.

6. Apparatus according to claim 1 including a tubular seismic streamersheath connected at one end to the pressure vessel outlet, and valvemeans connected to the other end of the sheath including a relief valveto hold a preset air pressure within the sheath.

7. Apparatus according to claim 5 wherein the valve means furtherincludes an inlet check valve through which air can be admitted topressurize the sheath.

8. Apparatus according to claim 7, the go-devil including a piston, alubricator ahead of the piston and a guide to the rear of the piston.

9. Method of operating the apparatus of claim 7 comprising maintaining apressure differential in the apparatus between the air in the pressurevessel and the air in the sheath tending to move the oil in the vesseland the go-devil in the sheath toward the valve means at the 7 8 end ofthe sheath and drawing the reel at desired speed expand the sheath topay out the harness. 11. Method of operating the apparatus of claim 8in- 10. Method of operating the apparatus of claim 7 cludingintroduction of lubricating oil into the sheath comprising maintaining aconstant above atmosphere in advance of the lubricator.

air pressure in the sheath in advance of the go-devil to

1. Apparatus for assembling a seismic streamer comprising a pressurevessel containing a rotatably mounted reel adapted to have a seismicstreamer harness wound thereon, said vessel being adapted to containoil, adapted for filling a seismic streamer sheath, and pressurized airover the oil, said vessel having an outlet adapted to be connected tosaid sheath for a seismic streamer and through which a harness wound onthe reel can extend, and means for drIving the reel at controlled speedto pay out the harness to such sheath.
 2. Apparatus according to claim 1having a seismic streamer harness wound on the reel and having attachedto the free end of the harness a go-devil comprising a piston adapted toseal with the inner periphery of said sheath and a lubricator in advanceof the piston.
 3. Apparatus according to claim 2 in which the lubricatorincludes a hub having a plurality of circumferentially overlappinghelical ribs thereabout.
 4. Apparatus according to claim 3 wherein thehub is rotatably mounted about the go-devil axis.
 5. Apparatus accordingto claim 2 including a tubular seismic streamer sheath connected at oneend to the pressure vessel outlet and closed at the other by a constantpressure relief valve, the go-devil being disposed in said sheath, and aquantity of lubricating oil being disposed in said sheath between thepiston and said relief valve.
 6. Apparatus according to claim 1including a tubular seismic streamer sheath connected at one end to thepressure vessel outlet, and valve means connected to the other end ofthe sheath including a relief valve to hold a preset air pressure withinthe sheath.
 7. Apparatus according to claim 5 wherein the valve meansfurther includes an inlet check valve through which air can be admittedto pressurize the sheath.
 8. Apparatus according to claim 7, thego-devil including a piston, a lubricator ahead of the piston and aguide to the rear of the piston.
 9. Method of operating the apparatus ofclaim 7 comprising maintaining a pressure differential in the apparatusbetween the air in the pressure vessel and the air in the sheath tendingto move the oil in the vessel and the go-devil in the sheath toward thevalve means at the end of the sheath and drawing the reel at desiredspeed to pay out the harness.
 10. Method of operating the apparatus ofclaim 7 comprising maintaining a constant above atmosphere air pressurein the sheath in advance of the go-devil to expand the sheath. 11.Method of operating the apparatus of claim 8 including introduction oflubricating oil into the sheath in advance of the lubricator.